Electric machinery such as, motors and generators, is conventionally impregnated with impregnation compounds. These compounds include varnishes, polyesters, polyamides and epoxies. The compounds are resin based. The main function of the resin is to mechanically restrain wires, such as windings contained within the slots of the rotor and stator of electric motors or generators, and a secondary function is to provide electrical insulation between the wires and the metallic slots and to provide thermal conductivity of heat away from the wires.
Two processes are conventionally used for impregnating electric machinery such as rotors and stators of electric motors and generators with resin based compounds. In a first process, the parts to be resin impregnated are dipped into a tank containing the resin. A combination of vacuum and/or pressure is used to force the resin into the desired areas to be impregnated such as in the slots containing the electric windings. After the dipping has been completed and the resin is heat cured as a consequence of thermal setting resins being conventionally used in this process, excess resin must be cleaned from the impregnated parts. This process is costly in implementation. A second process, known as the trickle impregnation process, utilizes heated resin which is heated to a temperature sufficient to reduce viscosity to permit flow along the wires of the electrical parts being impregnated which may be heated to cause impregnation of the slots and wires with the resin. Capillary action works on the resin to draw the resin into the interstices in the areas to be filled in the slots such as in between the wires. The disadvantage of this process is that it can only be utilized with resins which have a sufficiently low viscosity, such as 50-2500 cp. Many high performance resins have a higher viscosity especially after they have been mixed for several days with viscosity ranges such as 70,000 cp being possible. The second process suffers from the further disadvantage that the volume of resin which is used is not readily controlled as a consequence of no containment vessel being used. Furthermore, it is difficult to achieve a uniform coating of resin in areas of the electric machinery to be impregnated with the resin. Finally, the flow of resin onto selected areas of the electric machinery to be impregnated is difficult to control as a consequence of no containment vessel being used which is shaped to a contour of areas which are desired to be impregnated with resin.
U.S. Pat. No. 2,632,211 discloses a system for resin impregnating coils of electric machinery. The coils to be resin impregnated are held in an elastomeric mold. The resin is injected with a hollow tube underneath the turns of the wrapping of the coil until the resin begins to escape. Thereafter, the mold is pressurized causing deformation of the elastomer which prevents any substantial amount of resin from escaping from the coil. Thereafter, the mold is heated to cure the resin. This system has the disadvantage of relying upon pressure for introducing the resin underneath the turns of the wrapping of the coil. As a result of the resin being unheated, the energy necessary for causing the resin to flow in contact with the electric coils must be supplied either from pressure from the resin source or capillary action. Furthermore, the temperature of the coils which are placed within the mold cavity is not elevated. As a result, the viscosity of the resin is not lowered by contact with the electric coils which lessens the effect of capillary action and requires pressure to force the resin into the interstices of the windings.